Method for making carbamates

ABSTRACT

A process for the manufacture of alkyl carbamates from urea and aliphatic alcohols. The process is carried out under a vacuum, preferably at least 20 inches, and preferably in the presence of magnesium oxide catalyst.

This is a continuation, of application Ser. No. 263,880 filed May 15,1981, now abandoned which in turn is a continuation of application Ser.No. 83,514 filed Oct. 10, 1979, now abandoned.

The present invention relates to the manufacture of alkyl carbamatesfrom urea and aliphatic alcohols. In accordance with the invention, avacuum is applied, and preferably a magnesium catalyst is used. Thevacuum significantly accelerates the reaction, thereby reducing the costof manufacture.

BACKGROUND OF THE INVENTION

Alkyl carbamates are useful as intermediates for making textilecross-linking resins and as intermediates in the manufacture ofpharmaceuticals. A number of procedures for manufacturing them have beendescribed, e.g., in U.S. Pat. No. 3,574,711. In particular, it is knownto manufacture them by reaction of urea with an aliphatic alcoholaccording to the reaction:

    R--OH+NH.sub.2 CONH.sub.2 →ROCONH.sub.2 +NH.sub.3

U.S. Pat. No. 2,837,571 describes the use or cupric salts as catalystsfor this reaction. U.S. Pat. No. 3,574,711 discloses the possibility ofconducting the reaction without a catalyst and also the use of zinccatalysts such as zinc acetate, zinc formate, zinc carbonate, or zincoxide. These prior patents disclose heating the reactants at elevatedtemperatures such as 110° to 200° C. at atmospheric pressure. Liberatedammonia may be collected, e.g., in a dry ice trap. Following completionof the reaction, the products are recovered by distillation, e.g., undervacuum.

SUMMARY OF THE INVENTION

In accordance with the present invention, it has been found that theapplication of vacuum to the reaction accelerates the reaction whencarried out either without catalyst or using catalyst describedpreviously. Furthermore, it has been found that the reaction can beaccelerated by magnesium compounds. The use of vacuum when magnesiumcompounds are employed, has produced an especially useful effect.

DETAILED DESCRIPTION

The invention is applicable to a wide variety of alcohols i.e., alcoholshaving the formula R(OH)_(n) wherein R is an organic group and n is awhole number. R may be an aliphatic group, saturated or unsaturated, orit may be aromatic or arylaliphatic. However, the invention isparticularly applicable to higher alcohols which are not excessivelyvolatile under the temperature and pressure conditions applied in thereaction. For example, using a vacuum of 28 inches, isopropyl alcoholwas found to be too volatile. The invention is applicable to alcoholscontaining one, or more than one, hydroxyl group. The invention isparticularly useful with diethylene glycol, whose carbamate isparticularly suited for the manufacturing of textile resins.

The vacuum applied should be sufficient to accelerate the rate ofreaction. In this specification, vacuum is given in inches of mercury.)A vacuum of 10 inches or more may be used. It has been found, however,that at 10 inches, the condenser used to trap entrained alcohol becameclogged with a solid, which may be ammonium carbamate. This problem wasnot encountered at higher vacuums, such as 20-28 inches. Especiallyuseful results may be achieved at 28 inches, although it is believedthat still higher vacuums may be beneficial and economically useful.

The vacuum selected must be related to the vapor pressure of the alcoholwhich may be affected by dissolved urea and/or carbamate. If the vaporpressure is too high, the alcohol may be entrained with escaping ammoniato an excessive degree. To some extent this problem may be controlled bypassing the effluent from the reaction through a condenser which trapsalcohol, and the trapped alcohol may be returned to the reaction vessel.However, too high a vacuum may, in the case of some alcohols, cause toomuch entrainment.

One of the advantages of the present invention is that it may be carriedout at molar ratios of urea to alcohol that are very nearly 1:1. Usingsuch ratios, a relatively uncontaminated product may be obtaineddirectly, with little or no need for purification. The preferred ratiois 1.1 moles urea for each mole of alcohol. However, it will beappreciated that other ratios may be used, including excess of eitheralcohol of urea. The temperature of the reaction has not been found tobe critical. Initially, a temperature of 150° C. was thought to bepreferable, but a temperature of 160° C. is now preferred. Still highertemperatures may be used, e.g., up to 200° C. However, the increasedrate of reaction achieved must be evaluated against the increased energycost of such high temperatures. Conversely, lower temperatures may beused, e.g., down to 130° C., although slower reactions result from lowertemperatures.

The process under vacuum may be conducted with no catalyst. However, thereaction speed is increased with catalyst. Conversely, the proportion ofthe starting materials which react in a selected cycle time is increasedwith catalysts.

A preferred catalyst is a magnesium compound, especially magnesiumoxide. Magnesium oxide is supplied in various grades, according toreactivity, which in turn depends on degree of calcination. The gradesare characterized by the speed with which they neutralize acid. Thegrades are understood to differ in their degree of calcination, hardnessand granularity. For purposes of the present invention, high reactivitytypes are preferred. Particularly useful is Magox 98HR, supplied byBasic Chemicals, a division of Basic Incorporated, Cleveland, Ohio. Itis characterized by the following properties:

CHEMICAL COMPOSITION

    ______________________________________                                                       Typical                                                                              Minimum  Maximum                                        ______________________________________                                        Analysis                                                                      Loss on Ignition at 1370° C.                                                            5.0%              6.0%                                       Iodine No., meq/100 gms                                                                        45       35                                                  Chloride (as Cl) 0.2%              0.4%                                       Sulfate (as SO.sub.3)                                                                          0.55%             0.7%                                       Loss Proc Basis                                                               MgO              97.1%    97.0%                                               CaO              1.8%              2.0%                                       SiO.sub.2        0.6%              0.9%                                       R.sub.2 O.sub.3  0.5%                                                         PHYSICAL PROPERTIES                                                           Sizing               99.0%-200 mesh*                                          Bulk Density, Loose (approximate)                                                                  25 lbs./ft. 3                                            Cubic Displacement of 50 lb. Bag                                                                   1.6 ft.                                                  ______________________________________                                         *Also available 99%-325 mesh                                             

Other catalysts which may be used are calcium and zinc compounds such ascalcium oxide and zinc oxide.

The amount of catalyst used should be sufficient to increase the rate ofreaction. On the other hand, excessive amounts should be avoided, so asto minimize contamination of the product. The amount required for anyparticular reaction can be determined readily by a set of experimentsusing progressively increased amounts of catalysts.

The reaction may be carried out in a stirred flask or other reactionvessel with the required amount of urea and alcohol added at the start.The reactants are heated with steady heat until a desired reactiontemperature such as 150° C. or 160° C. is achieved. The reaction can befollowed, e.g. by measuring either ammonia evolution or unreacted urea.The flask preferably is fitted with a water cooled condenser to trapentrained alcohol so that it can be returned to the flask.

The carbamates are liquid at the reaction temperature. Therefore theymay be recovered by pouring into a container and allowed to solidify.

The following examples illustrate the practice of the invention. Unlessotherwise indicated, parts and percentages are by weight.

EXAMPLE I

Four experiments were conducted using 848 grams of diethylene glycol (8moles) and 528 grams of urea (8.8 moles). In each case, the reactionswere conducted at 28 inches vacuum. The reactants were heated withsubstantially identical heat input in a stirred flask, using awater-cooled Dean-Stark trap, until a temperature of 150° C. wasreached. Vacuum was applied to the flask through the trap. Trappedliquid was allowed to flow back into the flask. Then that temperaturewas maintained until the reaction was stopped.

The four experiments differed in the catalyst, as follows:

A. No catalyst

B. 0.75 gram magnesium oxide

C. 1.5 grams magnesium oxide

D. 1.5 grams zinc oxide

The experiments were followed and evaluated to produce the followingdata. In the tables which follow, temperature is given in °C., reactionrate in millimols per minute, residual urea in moles.

    ______________________________________                                                                    Residual                                                                             Ext. of                                    Time     Temp.   Rate       Urea   React                                      ______________________________________                                        EXPERIMENT A                                                                  8:42      98     0.2        8.791  0.000                                      9:00     120     6.2        8.734  0.007                                      9:15     131     15.7       8.570  0.025                                      9:30     137     26.9       8.251  0.061                                      9:45     140     33.5       7.798  0.113                                      10:00    142     36.5       7.273  0.173                                      10:15    144     33.3       6.750  0.232                                      10:30    144     34.1       6.244  0.290                                      10:45    145     33.1       5.740  0.347                                      11:00    146     31.6       5.255  0.402                                      11:15    147     30.1       4.793  0.455                                      11:30    148     29.1       4.349  0.505                                      11:45    149     26.5       3.932  0.553                                      12:00    149     26.2       3.536  0.598                                      12:15    150     24.8       3.154  0.641                                      12:30    150     21.8       2.805  0.681                                      12:45    150     15.4       2.526  0.713                                      13:00    150     14.1       2.305  0.738                                      13:15    150     12.8       2.103  0.761                                      13:30    151     12.6       1.913  0.782                                      13:45    150     10.5       1.740  0.802                                      14:00    150     9.1        1.593  0.819                                      14:15    150     7.7        1.466  0.833                                      14:30    151     7.4        1.353  0.846                                      14:45    151     6.0        1.252  0.858                                      15:00    150     4.6        1.172  0.867                                      EXPERIMENT B                                                                  8:50      99     0.0        8.791  0.000                                      9:15     124     11.9       8.643  0.017                                      9:30     133     24.6       8.369  0.048                                      9:45     138     32.6       7.941  0.097                                      10:00    140     36.0       7.427  0.155                                      10:15    141     36.2       6.886  0.217                                      10:30    142     37.3       6.334  0.279                                      10:45    143     37.6       5.773  0.343                                      11:00    144     35.2       5.227  0.405                                      11:15    145     34.0       4.708  0.464                                      11:30    146     31.5       4.216  0.520                                      11:45    148     30.8       3.748  0.574                                      12:00    149     29.5       3.296  0.625                                      12:15    150     27.9       2.865  0.674                                      12:30    149     21.9       2.491  0.717                                      12:45    150     20.7       2.172  0.753                                      13:00    151     18.8       1.875  0.787                                      13:15    151     16.1       1.614  0.816                                      13:30    151     12.7       1.398  0.841                                      13:45    150     9.3        1.233  0.860                                      14:00    149     7.3        1.108  0.874                                      14:15    150     5.6        1.011  0.885                                      14:30    151     4.6        0.934  0.894                                      14:45    148     1.4        0.889  0.899                                      15:00    148     1.4        0.868  0.901                                      EXPERIMENT C                                                                  9:33      99     0.0        8.791  0.000                                      10:00    125     15.2       8.586  0.023                                      10:15    132     28.2       8.261  0.060                                      10:30    135     35.8       7.781  0.115                                      10:45    137     38.8       7.221  0.179                                      11:00    138     40.1       6.630  0.246                                      11:15    140     40.0       6.030  0.314                                      11:30    140     39.5       5.433  0.382                                      11:45    142     38.8       4.846  0.449                                      12:00    144     36.1       4.284  0.513                                      12:15    144     35.3       3.748  0.574                                      12:30    146     33.0       3.236  0.632                                      12:45    148     30.0       2.764  0.686                                      13:15    150     21.9       1.985  0.774                                      13:30    151     16.5       1.697  0.807                                      13:45    150     12.5       1.480  0.832                                      14:00    150     10.9       1.304  0.852                                      14:15    150     8.0        1.163  0.868                                      14:30    150     7.4        1.047  0.881                                      14:45    151     6.5        0.943  0.893                                      15:00    150     4.4        0.861  0.902                                      15:15    149     3.3        0.803  0.909                                      15:30    150     1.8        0.765  0.913                                      15:45    151     1.6        0.739  0.916                                      16:00    150     0.7        0.722  0.918                                      EXPERIMENT D                                                                  8:20      99     0.0        8.791  0.000                                      8:44     125     13.1       8.634  0.018                                      8:55     132     21.8       8.442  0.040                                      9:04     137     30.3       8.207  0.066                                      9:16     140     36.1       7.809  0.112                                      9:35     142     38.4       7.101  0.192                                      9:56     144     36.9       6.311  0.282                                      10:21    146     35.9       5.401  0.386                                      10:45    148     33.9       4.565  0.481                                      11:10    150     31.1       3.753  0.573                                      11:40    151     28.9       2.854  0.675                                      12:10    151     18.4       2.145  0.756                                      12:40    150     11.4       1.698  0.807                                      13:10    151     10.2       1.374  0.844                                      13:40    150     6.2        1.129  0.872                                      14:10    151     4.3        0.971  0.890                                      ______________________________________                                    

EXAMPLE II

Four experiments were conducted in the same equipment as Example I, toevaluate the effect of various degrees of vacuu. In each case, thereactants were 848 grams diethylene glycol, 528 grams urea and 1.5 gramsmagnesium oxide. In each case, heat was applied at the same rate untilthe temperature reached 150° C. Then the temperature was maintained atabout 150° C. for 3 hours. After 3 hours, the amount of urea wasmeasured. It was found that the amount of urea decreased progressivelyas the pressure in the flask was reduced. (In two cases, the flask wasthen heated to 160° and reacted for two additional hours.) The vacuumsused were:

A. 20 inches

B. 25 inches

C. 26 inches

D. 27 inches

The heating schedules and residual urea measurements were as follows:

    ______________________________________                                        Time             Temp.                                                        ______________________________________                                        EXPERIMENT A                                                                  8:20              25° C.                                               9:12             110° C.                                               9:50             140° C.                                               10:25            146° C.                                               10:47            149° C.                                               10:55            150° C.                                               11:00            151° C.                                               11:25            151° C.                                               11:47            152° C.                                               11:55            152° C.                                               12:20            148° C.                                               12:35            147° C.                                               12:50            150° C.                                               1:00             151° C.                                               1:14             152° C.                                               1:55             151° C.                                                                              10.8% urea                                     EXPERIMENT B                                                                  8:14              25° C.                                               8:36              60° C.                                               8:47              76° C.                                               9:07             111° C.                                               9:30             133° C.                                               9:52             140+° C.                                              10:15            144+° C.                                              10:41            147° C.                                               10:56            150° C.                                               11:04            149+° C.                                              11:10            149° C.                                               11:36            151° C.                                               11:48            152° C.                                               12:08            149° C.                                               12:20            150° C.                                               12:32            151° C.                                               12:55            150° C.                                               1:05             149° C.+                                              1:45             151° C.                                                                              7.0% urea                                      2:10             148° C.                                               2:30             150° C.+                                              2:56             148° C.                                                                              6.28% urea                                     3:47             150° C.                                               EXPERIMENT C                                                                   7:55             25° C.                                               8:17              56° C.                                               8:43              99° C.                                               8:54             115° C.                                               9:05             125° C.                                               9:37             140° C.                                               10:36            147° C.                                               10:49            150° C.                                               11:15            151° C.                                               11:19            151°+ C.                                              11:30            151° C.                                               11:48            151°+ C.                                              12:15            150° C.                                               12:30            149°+ C.                                              12:43            150°+ C.                                              12:49            151° C.                                                                              5.92% urea                                     1:40             150° C.                                               1:49             150° C.                                                                              5.32% urea                                     2:20             160° C.                                               2:27             161° C.                                               2:49             160° C.                                                                              4.31% urea                                     3:49             160°+ C.                                              EXPERIMENT D                                                                  8:07              25° C.                                               8:25              50° C.                                               8:40              75° C.                                               8:54              99° C.                                               9:15             125° C.                                               9:50             140° C.                                               10:45            147° C.                                               11:10            150° C.                                               11:23            149° C.+                                              11:36            150° C.                                               11:42            151° C.                                               11:52            151° C.+                                              12:00            152° C.                                               12:10            150° C.                                               12:15            149° C.+                                              12:24            150° C.                                               12:28            150° C.+                                              12:35            151° C.+                                              12:40            152° C.                                               12:52            149°  C.+                                             1:00             149° C.                                               1:10             150° C.                                                                              4.98% urea                                     1:23             151° C.                                               2:10             150° C.                                                                              4.28% urea                                     2:22             150° C.                                               2:50             160° C.                                               3:10             160° C.                                                                              3.93% urea                                     ______________________________________                                    

EXAMPLE III

To compare the effect of various catalysts, experiments were conductedin the equipment described in Example I at 28 inches vacuum. In each,848 grams diethylene glycol (8 moles) were reacted with 528 grams urea(8.8 moles). The catalysts were as follows:

A. 1.5 grams magnesium oxide

B. 1.5 grams calcium oxide

C. 1.5 grams zinc oxide

The results demonstrated the superior effectiveness of magnesium oxide.

    ______________________________________                                        Ammonia        Time              Temp.                                        ______________________________________                                        EXPERIMENT A                                                                                    8:10             25° C.                                                8:25             51° C.                                                8:35             69° C.                                                8:45             84° C.                              0.0     g NH.sub.3 /min                                                                         8:54             99° C.                              0.271   g NH.sub.3 /min                                                                         9:16             125° C.                             0.496   g NH.sub.3 /min                                                                         9:27             132° C.                             0.733   g NH.sub.3 /min                                                                         9:42             137° C.                             0.831   g NH.sub.3 /min                                                                         10:25            142° C.                             0.792   g NH.sub.3 /min                                                                         10:45            143° C.+                            0.743   g NH.sub.3 /min                                                                         11:15            147° C.                             0.265   g NH.sub.3 /min                                                                         1:00             151° C.+                            0.166   g NH.sub.3 /min                                                                         1:30             151° C.                             0.121   g NH.sub.3 /min                                                                         2:00             150° C.                             0.080   g NH.sub.3 /min                                                                         2:30             150° C.                             0.071   g NH.sub.3 /min                                                                         3:00             150° C.                             0.068   g NH.sub.3 /min                                                                         3:30             151° C.                             EXPERIMENT B                                                                                    8:06             22° C.                                                8:25             56° C.                                                8:35             --                                                           8:40             84° C.                              0.048   g/min     8:50             99° C.                              0.199   g/min     9:15             122° C.                             0.445   g/min     9:30             135° C.                             0.771   g/min     10:00            142° C.                             0.758   g/min     10:30            145° C.                             0.703   g/min     11:00            148° C.                                               11:30            150° C.                             0.294   g/min     12:30            150° C.                             0.172   g/min     1:00             149° C.                             0.126   g/min     1:30             150° C.                             0.097   g/min     2:00             150° C.+                            0.027   g/min     2:30             150° C.                             0.046   g/min     3:00             150° C.                                               3:30                                                        OFF                                                                           EXPERIMENT C                                                                                    7:40             25° C.                                                8:00             65° C.                                                8:05             74° C.                                                8:12             86° C.                              0.0     g NH.sub.3 /min                                                                         8:20             99° C.                              0.229   g NH.sub.3 /min                                                                         8:44             125° C.                             0.377   g NH.sub.3 /min                                                                         8:55             132° C.                             0.521   g NH.sub.3 /min                                                                         9:04             137° C.                             0.621   g NH.sub.3 /min                                                                         9:16             140° C.                             0.658   g NH.sub.3 /min                                                                         9:35             142° C.                             0.635   g NH.sub.3 /min                                                                         9:56             144° C.                             0.613   g NH.sub.3 /min                                                                         10:21            146° C.                             0.577   g NH.sub.3 /min                                                                         10:45            148° C.                             0.534   g NH.sub.3 /min                                                                         11:10            150° C.                             0.499   g NH.sub.3 /min                                                                         11:40            151° C.                             0.320   g NH.sub.3 /min                                                                         12:10            151° C.                             0.201   g NH.sub.3 /min                                                                         12:40            150° C.                             0.178   g NH.sub.3 /min                                                                         1:10             151° C.                             0.114   g NH.sub.3 /min                                                                         1:40             150° C.                             0.095   g NH.sub.3 /min                                                                         2:10             151° C.                             ______________________________________                                    

EXAMPLE IV

The following experiment illustrates the use of sufficient urea to reactwith both hydroxl groups of diethylene glycol. The equipment used wasthe same as Example I, and the vacuum was 28 inches. The reactants were742 grams diethylene glycol (7 moles) 840 grams urea (14 moles), and 3grams magnesium oxide. The heating sequence was as follows:

    ______________________________________                                               Time         Temp.                                                     ______________________________________                                                8:07         54° C.                                                    8:30         77° C.                                                    8:47         96° C.                                                    9:08        119° C.                                                    9:34        132° C.                                                    9:53        135° C.                                                   10:10        137° C.                                                   10:32        138° C.                                                   10:58        140° C.                                                   11:17        141° C.                                                   11:47        145° C.                                                   12:10        147° C.                                                   12.32        149° C.                                                   12:36        150° C.                                                   12:47        151° C.                                                    1:03        151° C.+                                                   1:28        149° C.+                                                   1:35        150° C.                                                    1:50        152° C.+                                                   1:59        152° C.+                                                   2:31        151° C.                                                    3:28        152° C.+                                                   3:32        152° C.                                                    4:53        151° C.                                            ______________________________________                                    

The product contained 7.3% urea.

EXAMPLE V

In the equipment described in Example I, the following materials werereacted at 28 inches vacuum:

    ______________________________________                                        Neodol 253 (a hydroxyl-ended                                                                          668 grams                                             polyether derived from 3 moles                                                                        (2 moles)                                             ethylene oxide and a 12 carbon                                                atom alcohol)                                                                 Urea                    132 grams                                                                     (2.2 moles)                                           Magnesium oxide         2.4 grams                                             ______________________________________                                    

The heating sequence was as follows:

    ______________________________________                                               Time         Temp.                                                     ______________________________________                                               7:53          22° C.                                                   8:04         101° C.                                                   8:09         120° C.                                                   8:14         125° C.                                                   8:24         150° C.                                                   8:25         150° C.+                                                  8:34         151° C.                                                   8:42         150° C.                                                   8:53         151° C.+                                                  8:57         152° C.                                                   9:05         153° C.                                                   9:12         153° C.                                                   9:20         150° C.                                                   9:24         149° C.                                                   9:35         148° C.                                                   9:50         150° C.                                            ______________________________________                                    

EXAMPLE VI

In the equipment described in Example I, the following materials werereacted at 28 inches vacuum:

    ______________________________________                                        Neodol 253           200 grams                                                Diethylene glycol    600 grams                                                Urea                 414 grams                                                Magnesium oxide       3 grams                                                 ______________________________________                                    

The heating sequence was as follows:

    ______________________________________                                                Time Temp.                                                            ______________________________________                                                10:00                                                                               22° C.                                                           10:25                                                                               98° C.                                                           10:34                                                                              123° C.                                                           11:14                                                                              150° C.                                                           11:19                                                                              152° C.                                                           11:55                                                                              153° C.                                                           12:17                                                                              153° C.                                                           12:42                                                                              153° C.                                                            1:43                                                                              152° C.                                                            1:51                                                                              152° C.                                                            2:14                                                                              150° C.                                                   ______________________________________                                    

EXAMPLE VII

In the equipment described in Example I, the following materials werereacted at approximately 15 inches of vacuum:

    ______________________________________                                        methyl carbitol      480    grams                                             urea                 240    grams                                             magnesium oxide      1.5    grams                                             ______________________________________                                    

The heating sequence was as follows:

    ______________________________________                                               Time         Temp.                                                     ______________________________________                                                8:00         25° C.                                                    8:14         68° C.                                                    8:35        127° C.                                                    8:50        148° C.                                                    9:06        148° C.                                                    9:15        150° C.                                                    9:30        153° C.                                                    9:45        148° C.                                                   10:13        148° C.                                                   10:23        148° C.+                                                  10:27        150° C.                                                   10:37        151° C.                                                   10:42        152° C.                                                   10:57        152° C.                                                   11:00        153° C.                                                   11:10        152° C.+                                                  11:35        150° C.                                            ______________________________________                                    

EXAMPLE VIII

In the equipment described in Example I, the following materials werereacted at approximately 28 inches of vacuum:

    ______________________________________                                        butyl carbitol       525.6  grams                                             urea                 194.4  grams                                             magnesium oxide      1.5    grams                                             ______________________________________                                    

The heating sequence was as follows:

    ______________________________________                                                Time Temp.                                                            ______________________________________                                                 8:10                                                                               25° C.                                                            8:36                                                                              115° C.                                                            8:42                                                                              123° C.                                                            8:58                                                                              150° C.                                                            9:08                                                                              151° C.                                                            9:29                                                                              153° C.                                                            9:35                                                                              154° C.                                                            9:40                                                                              153° C.                                                            9:47                                                                              152° C.                                                            9:55                                                                              150° C.                                                           10:05                                                                              150° C.                                                           10:13                                                                              140° C.                                                           10:25                                                                              136° C.                                                           11:03                                                                              138° C.                                                           11:25                                                                              140° C.                                                   ______________________________________                                    

EXAMPLE IX

In the equipment described in Example I, the following materials werereacted at approximately 28 inches of vacuum:

    ______________________________________                                        Dow Corning Q43557    400    grams                                            (hydroxy group-containing                                                     silicone)                                                                     urea                  60     grams                                            magnesium oxide       0.5    grams                                            ______________________________________                                    

The heating sequence was as follows:

    ______________________________________                                               Time  Temp.                                                            ______________________________________                                               8:12   25° C.                                                          8:35  120° C.                                                          9:25  144° C.                                                          9:45  150° C.                                                          9:57  153° C.                                                          10:46 150° C.                                                   ______________________________________                                    

EXAMPLE X

In the equipment described in Example I, the following materials werereacted at 28 inches vacuum:

    ______________________________________                                        Dow Corning Q4-3667   400    grams                                            (hydroxy group containing                                                     silicone                                                                      urea                  22     grams                                            magnesium oxide       0.84   grams                                            ______________________________________                                    

The heating sequence was as follows:

    ______________________________________                                               Time  Temp.                                                            ______________________________________                                               8:11   25° C.                                                          8:35  120° C.                                                          8:48  147° C.                                                          8:50  151° C.                                                          8:52  155° C.                                                          8:55  159° C.                                                          8:57  154° C.                                                          9:02  146° C.                                                          9:05  146° C.                                                          9:10  151° C.                                                          9:14  154° C.                                                          9:16  157° C.                                                          9:25  148° C.                                                          9:37  146° C.                                                          9:54  152° C.                                                          10:26 140° C.                                                          11:00 152° C.                                                   ______________________________________                                    

EXAMPLE XI

In the equipment described in Example I, the following materials werereacted at 28 inches of vacuum (the vacuum was kept lower at the startof heating, and until foaming ended):

    ______________________________________                                        Sorbitol         438    grams (2.4 moles)                                     urea             162    grams (2.7 moles)                                     magnesium oxide  1.2    grams                                                 ______________________________________                                    

The heating sequence was as follows:

    ______________________________________                                                Time Temp.                                                            ______________________________________                                                 9:25                                                                              111° C.                                                            9:28                                                                              118° C.                                                            9:35                                                                              131° C.                                                            9:38                                                                              128° C.                                                            9:57                                                                              142° C.                                                           10:07                                                                              144° C.                                                           10:11                                                                              150° C.                                                           10:12                                                                              151° C.                                                           10:15                                                                              153° C.                                                           10:18                                                                              153° C.                                                           10:21                                                                              154° C.                                                           10:39                                                                              154° C.                                                           10:41                                                                              155° C.                                                           10:46                                                                              156° C.                                                           10:55                                                                              154° C.                                                           11:10                                                                              146° C.                                                           11:16                                                                              146° C.                                                   ______________________________________                                    

EXAMPLE XII

In the equipment described in Example I, the following materials werereacted at 28 inches vacuum:

    ______________________________________                                        Diethylene glygol    500    grams                                             Dow Corning Q4-3667  100    grams                                             Urea                 572    grams                                             Magnesium oxide      2.3    grams                                             ______________________________________                                    

The heating sequence was as follows:

    ______________________________________                                        Time                 Temp.                                                    ______________________________________                                        8:15                 on                                                       9:00                 149°                                              9:05                 150°                                              9:08                 152°                                              9:20                 145°                                              9:30                 152°                                              10:00                150°                                              10:30                150°                                              ______________________________________                                    

EXAMPLE XIII

In the equipment described in Example I, the following materials werereacted at 28 inches vacuum:

    ______________________________________                                        Diethylene glycol    848 grams                                                Urea                 528 grams                                                ______________________________________                                    

The experiment was conducted twice, using the following catalysts inrespective experiments:

A. magnesium oxide--1.5 grams

B. calcium oxide--1.5 grams

The heating sequences were as follows:

    ______________________________________                                               Time         Temp.                                                     ______________________________________                                        EXPERIMENT A                                                                          8:33         32° C.                                                    8:52         64° C.                                                    9:01         77° C.                                                    9:07         86° C.                                                    9:13         95° C.                                                    9:16        100° C.                                                    9:24        108° C.                                                    9:30        112° C.                                                    9:37        119° C.                                                    9:45        125° C.                                                    9:55        129° C.                                                   10:00        131° C.                                                   10:15        134° C.                                                   10:30        135° C.+                                                  10:45        136° C.+                                                  11:00        137° C.+                                                  11:15        138° C.                                                   11:30        139° C.                                                   11:45        140° C.                                                   12:00        141° C.                                                   12:15        142° C.                                                   12:30        143° C.                                                   12:45        144° C.+                                                   1:00        146° C.                                                    1:26        148° C.                                                    1:45        150° C.                                                    2:10        150° C.+                                                   2:23        151° C.                                                    2:37        151° C.                                                    2:45        150° C.                                                    3:05        148° C.                                                    3:40        152° C.                                            EXPERIMENT B                                                                          7:57         19° C.                                                    8:14         48° C.                                                    8:20         60° C.                                                    8:28         71°  C.                                                   8:43         94° C.                                                    8:52        105° C.                                                    9:04        119° C.                                                    9:15        127° C.                                                    9:30        134° C.                                                    9:45        137° C.                                                   10:00        138° C.+                                                  10:15        139° C.+                                                  10:30        140° C.+                                                  11:00        142° C.+                                                  11:15        143° C.+                                                  11:30        144° C.+                                                  12:15        148° C.                                                   12:45        150° C.                                                    1:00        150° C.+                                                   1:15        150° C.+                                                   1:30        151° C.                                                    1:45        150° C.                                                    2:00        150° C.+                                                   2:15        150° C.+                                                   2:30        152° C.                                                    3:00        148° C.                                                    3:15        148° C.+                                                   3:45        150° C.                                            ______________________________________                                    

In the first experiment, the urea content was reduced to 2.7% at 2:45whereas in the second experiment, the urea content was 4.17% at 1:45 and3:17% at 3:00. Therefore magnesium oxide was significantly moreeffective.

EXAMPLE XIV

In the equipment described in Example I, the following materials werereacted at 28 inches vacuum:

    ______________________________________                                        Polyethylene glycol (molecular                                                                       480    grams                                           weight 600) monomethyl ether                                                  Urea                   50     grams                                           Magnesium oxide        0.8    gram                                            ______________________________________                                    

The heating sequence was as follows:

    ______________________________________                                               Time  Temp.                                                            ______________________________________                                               8:15   35° C.                                                          8:40  140° C.                                                          8:45  148° C.                                                          8:50  152° C.                                                          8:56  153° C.                                                          9:06  149° C.                                                          9:12  147° C.                                                          9:23  152° C.                                                          9:28  154° C.                                                          9:45  150° C.                                                          10:25 154° C.                                                          10:30 150° C.                                                   ______________________________________                                    

It will be understood that the foregoing examples have been provided toillustrate the invention. No limitation thereto is intended, sincechanges may be made in details of composition and method of operationwithout departing from the scope of the invention.

What is claimed is:
 1. In a method for the manufacture of carbamates inwhich an alcohol is reacted with urea and ammonia is liberated, theimprovement wherein the reaction is carried out at a temperature of atleast 130° C., under a vacuum of at least 20 inches of mercury, saidalcohol having a volatility no greater than that of diethylene glycolunder the reaction conditions.
 2. A method as set forth in claim 1 inwhich the vacuum is 28 inches.
 3. A method as set forth in claim 1 inwhich the reaction is carried out in the presence of a catalyst selectedfrom the group consisting of calcium, zinc and magnesium compounds.
 4. Amethod as set forth in claim 3 in which the catalyst is selected fromthe group consisting of calcium oxide, zinc oxide and magnesium oxide.5. A method as set forth in claim 1 in which the alcohol is diethyleneglycol.
 6. A method as set forth in claim 3 in which the alcohol isdiethylene glycol.
 7. In a method for the manufacture of carbamates inwhich an alcohol is reacted with urea under a vacuum, the improvementwherein the reaction is carried out in the presence of magnesium oxideas a catalyst.
 8. A method as set forth in claim 7 in which a vacuum ofat least 20 inches is applied.
 9. A method as set forth in claim 8 inwhich a vacuum of 28 inches is applied.
 10. A method as set forth inclaim 8 in which the alcohol is diethylene glycol.